Now that JEDEC has published specification of GDDR7 memory, memory manufacturers are beginning to announce their initial products. The first out of the gate for this generation is Samsung, which has has quietly added its GDDR7 products to its official product catalog.
For now, Samsung lists two GDDR7 devices on its website: 16 Gbit chips rated for an up to 28 GT/s data transfer rate and a faster version running at up to 32 GT/s data transfer rate (which is in line with initial parts that Samsung announced in mid-2023). The chips feature a 512M x32 organization and come in a 266-pin FBGA packaging. The chips are already sampling, so Samsung's customers – GPU vendors, AI inference vendors, network product vendors, and the like – should already have GDDR7 chips in their labs.
The GDDR7 specification promises the maximum per-chip capacity of 64 Gbit (8 GB) and data transfer rates of 48 GT/s. Meanwhile, first generation GDDR7 chips (as announced so far) will feature a rather moderate capacity of 16 Gbit (2 GB) and a data transfer rate of up to 32 GT/s.
Performance-wise, the first generation of GDDR7 should provide a significant improvement in memory bandwidth over GDDR6 and GDDR6X. However capacity/density improvements will not come until memory manufacturers move to their next generation EUV-based process nodes. As a result, the first GDDR7-based graphics cards are unlikely to sport any memory capacity improvements. Though looking a bit farther down the road, Samsung and SK Hynix have previously told Tom's Hardware that they intend to reach mass production of 24 Gbit GDDR7 chips in 2025.
Otherwise, it is noteworthy that SK Hynix also demonstrated its GDDR7 chips at NVIDIA's GTC last week. So Samsung's competition should be close behind in delivering samples, and eventually mass production memory.
Source: Samsung (via @harukaze5719)
MemoryKioxia's booth at FMS 2024 was a busy one with multiple technology demonstrations keeping visitors occupied. A walk-through of the BiCS 8 manufacturing process was the first to grab my attention. Kioxia and Western Digital announced the sampling of BiCS 8 in March 2023. We had touched briefly upon its CMOS Bonded Array (CBA) scheme in our coverage of Kioxial's 2Tb QLC NAND device and coverage of Western Digital's 128 TB QLC enterprise SSD proof-of-concept demonstration. At Kioxia's booth, we got more insights.
Traditionally, fabrication of flash chips involved placement of the associate logic circuitry (CMOS process) around the periphery of the flash array. The process then moved on to putting the CMOS under the cell array, but the wafer development process was serialized with the CMOS logic getting fabricated first followed by the cell array on top. However, this has some challenges because the cell array requires a high-temperature processing step to ensure higher reliability that can be detrimental to the health of the CMOS logic. Thanks to recent advancements in wafer bonding techniques, the new CBA process allows the CMOS wafer and cell array wafer to be processed independently in parallel and then pieced together, as shown in the models above.
The BiCS 8 3D NAND incorporates 218 layers, compared to 112 layers in BiCS 5 and 162 layers in BiCS 6. The company decided to skip over BiCS 7 (or, rather, it was probably a short-lived generation meant as an internal test vehicle). The generation retains the four-plane charge trap structure of BiCS 6. In its TLC avatar, it is available as a 1 Tbit device. The QLC version is available in two capacities - 1 Tbit and 2 Tbit.
Kioxia also noted that while the number of layers (218) doesn't compare favorably with the latest layer counts from the competition, its lateral scaling / cell shrinkage has enabled it to be competitive in terms of bit density as well as operating speeds (3200 MT/s). For reference, the latest shipping NAND from Micron - the G9 - has 276 layers with a bit density in TLC mode of 21 Gbit/mm2, and operates at up to 3600 MT/s. However, its 232L NAND operates only up to 2400 MT/s and has a bit density of 14.6 Gbit/mm2.
It must be noted that the CBA hybrid bonding process has advantages over the current processes used by other vendors - including Micron's CMOS under array (CuA) and SK hynix's 4D PUC (periphery-under-chip) developed in the late 2010s. It is expected that other NAND vendors will also move eventually to some variant of the hybrid bonding scheme used by Kioxia.
Storage
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